Silt in the River Garden

Students explain a cause-and-effect chain in an environmental system and state the physical limit of an engineering solution.

Student Name: ______________________

Grade Band: Grades 6-8

Words

sediment. fine sand or clay carried by moving water Example: Storm runoff washed heavy sediment into the canal intake.
filter. a device with small openings that traps solid particles Example: Mateo cleaned the wire filter at the mouth of the pipe.
dissolved. mixed completely into a liquid so it cannot be seen as pieces Example: Road salt stays dissolved as it passes through a wire screen.
intake. the opening where water enters a pipe or pump Example: Fine clay clogged the intake pipe on Tuesday afternoon.
oxygen. a gas in water and air that plant roots need to stay healthy Example: Stagnant water holds less oxygen for the floating roots.
cause. the reason something happens in a system Example: Amina looked for the cause of the slow water flow.

Speaking plan

Present a scientific explanation linking the storm runoff to the wilted lettuce and specifying the boundary of mechanical filtration.

Trace the chain from storm silt to reduced flow and root oxygen.
Explain how rinsing the mesh restores circulation.
Contrast solid sediment with dissolved salt ions.

Writing plan

Write an engineering note for Mateo. Explain how storm sediment caused the lettuce wilt in Basin Three, and clarify why the 100-micron mesh solves the flow problem but not dissolved salt.

Connect the clogged intake mesh to flow rate and dissolved oxygen.
Cite the evidence sentence about wire holes and dissolved salt.
Use causal and contrastive connectors (because, so, although).

Guided frames

The lettuce roots lost oxygen because ___.
When Mateo rinses the filter, ___.
However, the mesh filter cannot remove ___ because ___.

Drafting & Evidence Sketch Space